Randomized clinical trial to evaluate the efficacy and safety of valganciclovir in a subset of patients with chronic fatigue syndrome

There is no known treatment for chronic fatigue syndrome (CFS). Little is known about its pathogenesis. Human herpesvirus 6 (HHV-6) and Epstein–Barr virus (EBV) have been proposed as infectious triggers.

VGCV patients experienced a greater improvement by MFI-20 at 9 months from baseline compared to placebo patients but this difference was not statistically significant. However, statistically significant differences in trajectories between groups were observed in MFI-20 mental fatigue subscore (P=0.039), FSS score (P=0.006), and cognitive function (P=0.025). VGCV patients experienced these improvements within the first 3 months and maintained that benefit over the remaining 9 months. Patients in the VGCV arm were 7.4 times more likely to be classified as responders (P=0.029).

In the VGCV arm, monocyte counts decreased (P?0.001), neutrophil counts increased (P?=?0.037) and cytokines were more likely to evolve towards a Th1-profile (P?0.001). Viral IgG antibody titers did not differ between arms.

VGCV may have clinical benefit in a subset of CFS patients independent of placebo effect, possibly mediated by immunomodulation and/or antiviral effect. Further investigation with longer treatment duration and a larger sample size is warranted.